Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F22—STEAM GENERATION
  • F22D—PREHEATING, OR ACCUMULATING PREHEATED, FEED-WATER FOR STEAM GENERATION; FEED-WATER SUPPLY FOR STEAM GENERATION; CONTROLLING WATER LEVEL FOR STEAM GENERATION; AUXILIARY DEVICES FOR PROMOTING WATER CIRCULATION WITHIN STEAM BOILERS
  • F22D1/00—Feed-water heaters, i.e. economisers or like preheaters
  • F22D1/40—Combinations of exhaust-steam and smoke-gas preheaters
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F22—STEAM GENERATION
  • F22D—PREHEATING, OR ACCUMULATING PREHEATED, FEED-WATER FOR STEAM GENERATION; FEED-WATER SUPPLY FOR STEAM GENERATION; CONTROLLING WATER LEVEL FOR STEAM GENERATION; AUXILIARY DEVICES FOR PROMOTING WATER CIRCULATION WITHIN STEAM BOILERS
  • F22D1/00—Feed-water heaters, i.e. economisers or like preheaters
  • F22D1/36—Water and air preheating systems
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23L—SUPPLYING AIR OR NON-COMBUSTIBLE LIQUIDS OR GASES TO COMBUSTION APPARATUS IN GENERAL ; VALVES OR DAMPERS SPECIALLY ADAPTED FOR CONTROLLING AIR SUPPLY OR DRAUGHT IN COMBUSTION APPARATUS; INDUCING DRAUGHT IN COMBUSTION APPARATUS; TOPS FOR CHIMNEYS OR VENTILATING SHAFTS; TERMINALS FOR FLUES
  • F23L15/00—Heating of air supplied for combustion
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23L—SUPPLYING AIR OR NON-COMBUSTIBLE LIQUIDS OR GASES TO COMBUSTION APPARATUS IN GENERAL ; VALVES OR DAMPERS SPECIALLY ADAPTED FOR CONTROLLING AIR SUPPLY OR DRAUGHT IN COMBUSTION APPARATUS; INDUCING DRAUGHT IN COMBUSTION APPARATUS; TOPS FOR CHIMNEYS OR VENTILATING SHAFTS; TERMINALS FOR FLUES
  • F23L15/00—Heating of air supplied for combustion
  • F23L15/04—Arrangements of recuperators
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E20/00—Combustion technologies with mitigation potential
  • Y02E20/14—Combined heat and power generation [CHP]
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E20/00—Combustion technologies with mitigation potential
  • Y02E20/34—Indirect CO2mitigation, i.e. by acting on non CO2directly related matters of the process, e.g. pre-heating or heat recovery
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S122/00—Liquid heaters and vaporizers
  • Y10S122/07—Feeding air

Definitions

• the invention relates to a steam power plant for generating electrical energy with a fossil-fired boiler, a water-steam circuit for generating high-voltage, superheated steam for a steam turbine, an economizer for transferring flue gas heat to feed water, and an air preheater for transferring Flue gas heat on fresh air and with facilities for dedusting, desulfurization and possibly denitrification of the flue gases.
• a further disadvantage is that in power plants in which there is no possibility for further use of the residual heat still present at a relatively high temperature level in the flue gas leaving the air preheater, be it through Reheating of the cleaned flue gases before entering the chimney, or whether it is by decoupling heat for district heating purposes, is destroyed in the flue gas desulfurization system, which leads to a further reduction in the overall efficiency of the power plant.
• the known steam power plants of the type mentioned are not optimal in their starting behavior.
• a coal-fired plant for example, before the coal firing is started up, considerable amounts of expensive auxiliary fuel oil or gas must be burned in the boiler until the parts of the plant to be warmed up by means of flue gas heat, e.g. the mills for the mill drying of the coal, the catalytic denitrification reactor and the air preheater with its large regenerative heat storage masses have reached the required minimum operating temperature;
• the steam generated during the start-up but also during the shutdown phase is generally deposited in the condenser of the steam power plant without using heat.
• the object of the invention is to reduce energy losses in a system of the type mentioned at the outset, to improve the use of heat by the flue gas and to start up by using less oil or gas and more sensibly using the steam generated in the start-up phase as a whole to make it more economical
• this object is achieved by a steam power plant, which is characterized by a first heat exchanger system with a cross section through which recirculation air flows and a cross section through which a heat transfer medium flows.
• the air-guiding cross-section is connected on the inlet side to the fresh air outlet of the air preheater and on the outlet side to the fresh air inlet of the air preheater.
• the measures proposed according to the invention lead to a significant reduction in exergy losses in the air preheater compared to the prior art, to a significantly improved use of the heat contained in the flue gas and thus to a significant increase in the overall efficiency of such a steam power plant.
• the heat flow capacities in the two heat exchanger cross sections of the air preheater can be largely harmonized with the result of small temperature differences both at the warm and at the cold end and accordingly reduced exergy losses.
• the fresh air can also be supplied preheated to the air preheater, ie also the residual heat still contained in the flue gas before desulfurization can now be used in the overall process as a result of the transfer to the fresh air in the second heat exchanger system provided in accordance with the invention, with the result that the efficiency is further improved.
• the invention proves to be particularly advantageous in power plants in which the desulfurized cold flue gases are introduced directly into the cooling tower of the power plant and are discharged into the atmosphere together with the cooling air and a decoupling of residual flue gas for district heating purposes or other purposes is not provided.
• the circuit according to the invention allows the residual heat still contained in the flue gas to be fed back to the power plant cycle process in full under thermodynamically favorable conditions.
• an improvement in the degree of efficiency can be achieved according to a further feature of the invention in that now the fresh air is preheated in a steam-air preheater by transferring low-temperature heat from the water-steam cycle before entering the air preheater.
• the system concept according to the invention generally makes it possible to raise the low-temperature heat generated in the power plant to a higher temperature level by transferring it to the fresh air and coupling it into the air preheater and to supply it again to the water-steam cycle.
• the first heat exchanger system is used as a starting heat exchanger.
• the regenerative heat storage masses of the air preheater can be preheated even before the start-up process of the steam power plant, ie before the burners in the boiler are ignited.
• heat is transferred in the start-up heat exchanger from any heat transfer medium to the recirculation air, which is conducted in the circuit between the still cold air preheater and the start-up heat exchanger, and the regenerative heat storage masses of the air preheater are heated up in the process.
• the fresh combustion air flowing into the boiler via the air preheater is heated accordingly, with advantageous effects both during a cold start with the boiler heating surfaces already cooled and during a hot start with the boiler heating surfaces still hot.
• the system heats up faster, i.e. oil or gas can be saved in the boiler, while there is less subcooling during the hot start due to the incoming cold combustion air.
• Another advantage due to the preheating of the air preheater results from the fact that when the air preheater is not desulfurized the first time it is acted on Flue gas too much cooling with a corresponding drop below the dew point is avoided, with the consequence of correspondingly reduced corrosion in the air preheater and in downstream system parts, for example the electrostatic filter.
• the start-up heat coupled into the air preheater via the start-up heat exchanger can - as already mentioned - come from any source.
• it can be heat from another steam power plant available at the same location or waste heat from another industrial plant.
• feed water from the feed water tank of the water-steam cycle is used as the heat carrier, which has already been brought to temperature by means of start-up steam from self-generation, from neighboring plants or separate boilers .
• the temperature of the withdrawn feed water can be increased further in a further heat exchanger in the heat exchange with condensing start-up steam before it cools down in the start-up heat exchanger.
• FIG. 1 shows an example of a circuit arrangement for reducing heat losses when operating a steam power plant.
• FIG. 2 shows an example of a circuit arrangement for reducing heat losses when starting a steam power plant.
• hot flue gas from a steam generator of a coal-fired power plant is first fed to a denitrification plant 2 via a line 1 and then to an air preheater 3 at a temperature of approximately 380 ° C.
• the air preheater 3 the flue gas is cooled to about 130 ° C. in the heat exchange with air.
• the cooled flue gas is then fed into a flue gas desulfurization system 8 via a line 7 and finally discharged into the atmosphere together with the cooling air via the cooling tower of the power plant (not shown here).
• the combustion air required in the steam generator is fed to the power plant via a line 9 and a blower 10 and is first preheated to a temperature of approximately 70-80 ° C. in a heat exchanger 11.
• the heat required for preheating is transferred from the heat exchanger 6 into the heat exchanger 11 by means of a closed circuit water system 12.
• the fresh air preheated in the heat exchanger 11 is mixed in at a mixing point 13 recirculation air, the temperature and mass flow of which are dimensioned such that a heat flow equilibrium is approximately established in the air preheater 3, ie that both at the cold and at the warm end of the air preheater now have the desired small temperature differences between the flue gas and the air.
• the recirculation air flow is again separated from the fresh air flow at a branch point 14.
• the recirculation air in a first heat exchanger system is first in a heat exchanger 16 in heat exchange with high pressure feed water and, if necessary, in a further heat exchanger 17 in Heat exchange with low-pressure feed water cooled again and conveyed back to the mixing point 13 via a controllable fan 18.
• FIG. 2 shows schematic sections from the circuit of a coal-fired steam power plant.
• hot flue gas is fed from an economizer 21 of the steam generation system via line 22 to a catalytic denoxification reactor 23 and finally to an air preheater 24.
• the flue gas is cooled in the heat exchange with feed water to the optimal operating temperature of the denitrification reactor 23 of approximately 350-380 ° C. The further cooling to about 130 C then takes place in the heat exchange with fresh combustion air in the downstream.
• Air preheater 24 After it has cooled, the flue gas is dedusted or desulphurized in facilities not shown here and then e.g. via a cooling tower, also not shown, is discharged into the atmosphere together with cooling air.
• the combustion air required for the boiler is fed to the system via a line 25, heated to about 350 ° C. in the air preheater 24 and then passed via a line 26 to the furnace or to the mill drying.
• the section of the water-steam circuit shown in the system shows a feed water tank 27 into which the condensate, which flows in via a line 28, is heated with steam from line 29.
• the heated water (feed water) is withdrawn from the feed water container 27 via a line 30, pumped to about 250-300 bar in a high pressure pump 31, then in a conventional high pressure preheater section 32 to a temperature of about 250-300 ° C.
• the preheated feed water flows via a line 33 into the economizer 21, in which it is further heated in the heat exchange with hot flue gas, via a line 34, the feed water is then passed into the further heat exchanger system of the boiler and evaporated there or overheated to the inlet temperature of the steam turbine of about 530 - 580 ° C.
• the water vapor After the expansion in the turbine, the water vapor is condensed and fed again to the feed water tank 27 via the line 28.
• a start-up heat exchanger 35 with a cross section through which recirculation air flows is provided, which is connected on the input side to the fresh air outlet via a line 36 and on the output side via a line 37 and a blower 38 to the fresh air inlet of the air preheater 24.
• the recirculation air circulated between the air preheater 24 and the start-up heat exchanger 35 is heated in the start-up heat.
• Exchanger 35 is heated and cooled again in the air preheater 24, the regenerative heat storage masses of the air preheater heating up.
• this preheating has the result that the flue gas which arises at the start of the start-up process is cooled to a lesser extent in the air preheater, so that the temperature drops below the dew point and the associated corrosion damage in the air preheater and downstream system parts can be prevented.
• the recirculation air of the heat exchanger 35 is heated in the heat exchange with hot feed water, which in the feed water tank 27 by injecting start-up steam supplied via a line 29 via lines 39, 40, 41 with the respectively open valves 42 and 43 are withdrawn, cooled in the heat exchanger 35 and then returned to the feed water container 27 via lines 44 and 45 and the opened valve 46.
• the feed water can be further heated before entering heat exchanger 35 by at least a partial flow of the heated feed water flowing in line 39 via a valve 47 now opened and a line 48 into a further heat ⁇ exchanger 49 is initiated. Heating the heat exchanger - left
• shear 49 takes place by condensing start-up steam from a source 50, which is then introduced into the feed water tank 27 via a line 51.
• the feed water flow which is further heated in the heat exchanger 49 is first introduced into the line 41 and then into the heat exchanger 35 via a line 52 and an open valve 53.
• additional heat is supplied not only to the air preheater 24 but also to the economizer 31 when the steam power plant is started up.
• at least a partial flow of the feed water heated in the heat exchanger 49 is fed via an open valve 54 and the lines 44 and 55 into the line 33 and mixed there with feed water from the high-pressure preheater section 32.
• start-up heat can be used. Due to the rise in temperature of the feed water, the flue gas in the economizer cools down less during the start-up process, so that the minimum temperature for starting the downstream denitrification reactor 23 is reached more quickly.
• the heat transfer to the storage mass of the air preheater 24 or the additional heat transfer to the combustion air or to the feed water also enables the heat of the steam generated in the start-up phase to be used; the storage in the air preheating heating surfaces 4 also enables the steam generated during the start-up phase to be used.
• the proposed coupling of additional heat into the economizer proves to be useful not only during the start-up process of the system, but it can also be used, for example, in the low-load operation of the power plant Support of the flue gas temperature and thus to maintain the optimal operating temperature of the denitrification reactor 23 can be used.
• the flue gas temperature after the air preheater 24 can be kept constant in the entire load range; an optimal lower flue gas temperature is thus possible even at full load, without, e.g. at partial load, unacceptable low temperatures and therefore corrosions.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Air Supply (AREA)
• Engine Equipment That Uses Special Cycles (AREA)
• Chimneys And Flues (AREA)

Applications Claiming Priority (5)

Publications (2)

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Family Applications (1)

Country Status (8)

Cited By (1)

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• 1993
  • 1993-10-15 DE DE4335216A patent/DE4335216C2/de not_active Expired - Lifetime
• 1994
  • 1994-05-09 WO PCT/DE1994/000530 patent/WO1994027089A2/fr not_active Ceased
  • 1994-05-09 CA CA002139875A patent/CA2139875A1/fr not_active Abandoned
  • 1994-05-09 RU RU95105164/06A patent/RU95105164A/ru unknown
  • 1994-05-09 DE DE59407588T patent/DE59407588D1/de not_active Expired - Lifetime
  • 1994-05-09 AT AT94914332T patent/ATE175487T1/de not_active IP Right Cessation
  • 1994-05-09 EP EP94914332A patent/EP0648323B1/fr not_active Expired - Lifetime
  • 1994-05-09 JP JP6524811A patent/JPH08502345A/ja active Pending
  • 1994-05-09 US US08/367,163 patent/US5687674A/en not_active Expired - Fee Related

Non-Patent Citations (1)

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